An apparatus for grinding the inner surface and/or the outer surface of an annular workpiece, especially the race rings for antifriction bearings can include a non-rotating holder which serves to position the annular workpiece for the grinding operation. The apparatus also includes a rotating driver which is powered to rotate about its axis, and further includes a pressing device which urges the workpiece ring against the driver.
The workpiece holder hydrodynamically centers the workpiece for the grinding operation while forming a fluid bearing on which it is journaled with the workpiece during such operation then being pressed at end face by the pressing device, against an end face of the rotating driver.
The workpiece and the rotating driver can thus be rotated or turned together, with the workpiece being coaxially aligned with respect to the rotating driver.
The pressing device can include a hydraulic pressing cylinder/piston assembly which acts against the workpiece on the side opposite to the driver, i.e. the workpiece is generally disposed between the pressing device and the driver.
The hydrodynamic centering holder for the workpiece, can include a holder shaft for grinding outer surfaces, or a holder bed or sleeve for the grinding of inner surfaces. The outer diameter of the holder shaft is smaller than the inner diameter of the workpiece, to create a centering or annular clearance gap. Similarly, the holder sleeve can have an inner diameter which is greater than the outer diameter of the workpiece, also to create an annular clearance.
The centering action is achieved by continuous introduction of a hydraulic pressure medium into the clearance. In general, the conventional grinding or cooling medium or liquid is also used as the hydraulic pressure medium for this centering or conversely this centering medium forms the grinding and cooling medium. The hydraulic pressure medium is introduced through corresponding bores or passages in the hydrodynamic centering holder.